High Blood Pressure, Not On Any Medicine, Swollen Bruise Below Knee Joint Hurts. Treatment?

Hello, My name is Rhonda and I m 48 years old. I don t take medications and I do have elevated high blood pressure . My height is five feet and I weigh 180. My question is I have a a large bruise the size of a small cookie on the back of my leg a little below the knee joint . It is dark purple and does not hurt. Now, I have noticed them before maybe 6 or 7 years ago. It occurred after a very long strenuous walk. But, on that occasion it hurt and was swollen. Since then I a get occasional bruising here and there nothing to the degree of the bruise I have today. I didn t hit myself and I m just worried about clots and that nature. Thank You, Rhonda